Resistance element



June 7, 1932. H, E CAMIPBELL 1,861,434

' RESISTANCE ELEMENT Filed May 4. 1927 Patented .June 7, 1932 UNITED STATES PATENT "orics HARRY E. CAMPBELL, O1 MILWAUKEE, WISCONSIN, ASSIGNOB, BY MESNE ASSIGN- MENTS, TO CUTLER-HAMMER,

INC., A CORPORATION OF DELAWARE RESISTANCE ELEMENT Application filed. ma 4, 1927. Serial No. 188,785.

This invention relates to resistance elements more particularly adapted'for use with electric controllers and starters of venous kinds.

It is one of the objects of the present invention to provide a resistance element formed of sheet metal cut in a'manner to form a zig-zag formation and to permit expanding the portions to provide ample ventilation in use.

A further object of the invention is to provide a resistance element formed of expanded sheet metal having means of support which .the insulation of the supp will rigidly maintain all portions of the ele ment in firm position.

A further object of the invention is to provide a. resistance element having insulating means for supporting the difierent portions of the element and also for preventing said portions from abrading or cutting through ort.

A further object ofv the invention is to provide a resistance element having terminals which are also formed of commercial metal and are easily connectible to the element.

A further object of the invention is to provide a resistance element which when expanded will automatically position the ends of the zigzag portions in regular spaced position..

A further object of the invention is to provide a resistance element which is of simple construction, is strong and durable and is well adapted for the purpose described.

With the above and other objects in view the invention consists of the improved resistance element and itsparts and combinations asset forth in the claims, and all equivalents thereof.

In the accompanying drawing in which the same reference characters indicate thesame parts in all of the views:

Fig. 1 is a side view of one of the improved resistance elements;

Fig. 2 is a transverse sectional view thereof taken on line 2-2 of Fig. 1-;

Fig. 3 is a side view of the resistance member after it has been cut, but before being expanded to shape in which it is used;

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Fig. 5 is an edge view of the terminal memher; and

Fi 6 is a. sectional detail view of a modified orm showing means for protecting the insulation of the support from the edges of the resistance member. Referring to the drawing the numeral 8 indicates a plate of sheet metal having suitableresistance qualities which is formed with transverse slits 9 extending alternately inwardly from its opposite side edges to the stop apertures or holes 10. The plate 8 is also provided'with slit-intersecting apertures or holes 11 andlarger end openings 12 for receiving supporting bars 13 when thev plate of metal is expanded endwise as illustrated in Fig. 1. The bars 13 are covered with tubes of suitable insulating material 14 to electrically insulate the staggered end portions 15 from each other when assembled on the bars. The end portions of the bars are extended through U-shaped end bracket members 16 and are connected thereto by nuts 17 which are threaded on the rod ends on each side of each end member. The nuts on the inner sides of the end members bear against the ends of the insulating tubes and prevent endwise movement of said tubes. The end flanges 16 of the end bracket members are provided with bolt openings 18 for mounting the resistance elements singly frame (not shown). In expanding the plate endwise the end portions 15 will turn at an angle as indicated in Fig. 1 so that theinsulated rods may be inserted through the end openings 12 and when released the tendency of the plate to assume its fiat unexpanded position will cause the end portions to tightly engage the insulating tubes and maintain the parts in expanded position. Furthermore, the expansion will separate each slit part a sufiicient distance to insulate the parts from each other and permit a free circulation of air therebetween to dissipate the heat from the plates.

The end portions 15 of the plate in being moved to an angular position will cause each leg 19 (formed by the slits) to flex or-bend or in a bank to a- CO a laterallylin forming the zigzag construction so that each leg is partially twisted as clearly indicated in Figs. 1 and 2. This twisting is facilitated by the small openings 1-0 and permits alining the openings 12 to pass the insulated rods 13 therethrough. The small openings 10 also reduce the width of the legs at points adjacent the large openlngs so that the resistance at said points will be approxlmately the same as at other portlons of the legs. The opposite terminal end legs 15 of the plate are enclosed between two terminal members 20 and clamped thereto by screws 21 which extend through the half openings 10 in the opposite edges of the terminals 15 as clearly shown in Flg. 4. The outer edge portions of the terminal members 20 are flanged outwardly in opposite directions as indicated by the numeral 22 to reinforce the said portions. A third terminal member 23 having a V-shaped groove 24 is placed on one side of the members 20 and is connected thereto by a bolt 25 which extends through the three members and, is provided with a nut 26. Each member 20 is formed with a slot 27 extending in opposite directions with relation to each other to. accommodate the insulated rod 13 extending through the openings 12 of the terminal ends of the plate. The slotted portions of the members 20 are formed with angular side flanges 28 shaped to fit the insulating rods 13 when the parts are assembled together. The V-shaped groove portions 24 and the members 20 provide for connecting a circuit car'- rying current thereto.

When the leg portions are expanded and mounted on the insulating bars, the said bars will, due to the lateral flexing of the legs, maintain the parts in expanded position. In the modified form shown in Fig. 6 a metal thimble 29 is extended through the opening or eye 12 in each leg end except the terminal ends 15 and slipped over the insulated rods to prevent the leg portions from cutting through the insulation of the rods and shortcircuiting the legs of the plate. The openings or eyes 12 are slightly larger than the diameter of the end flanges 29' of the thimbles to permit extending the thimbles therethrough, but when the legs 15 are turned at an angle with relation to the thimble as shown the thimble will be firmly held against endwise movement in said leg, and the thimble will prevent the" legs fromcutting the insulating material. It is to be understood that plates may be formed of any thickness of metal to provide the required resistance, and a number of the plates may be connected together to form banks in any manner desired. It is also to be understood that the terminal members may be connected to any of the leg portions of the member intermediate of the outer terminal end legs.-

From the foregoing description, it will be seen that the resistance element is of very simple construction and is well adapted for the purpose described.

What I claim as my invention is: v

1. As an article of manufacture, a resistance element of slitted sheet metal, said element comprising strips and connecting portions at the outer ends of the strips, said connecting portions at the respective ends of the strips being alined in spaced parallel planes displaced in like directions substantially less than ninety degrees from the initial plane thereof, whereby said element is expanded with the adjacent strips. arranged in crisscross or laterally zigzagged relation to each other, and a pair of supporting members frictionally engaged by said connecting portions whereby said element is maintained in expanded condition.

2. As' an article of manufacture, a resistance element formed from a sheet metal plate having parallel slits extending inwardly from opposite sides in staggered relation to each other to provide strips and connecting portions at the outer ends of the strips, said plate being provided with relatively large openings within each of said connecting portions and with relatively smaller openings coincident with the respective slits at the inner ends of the latter and on opposite sides of the respective connecting portions, said connecting portions being alined in parallel planes displaced in like directions substantially less than ninety degrees from the initial plane thereof, whereby said element is expanded with the adjacent strips arranged in crisscross or laterally zigzagged relation to each other,and a pair of one-piece insulating supporting elements penetrating said relatively large openings and fri-ctionally engaged bythe walls of the latter to retain said element in expanded condition.

3. As an article of manufacture, a resistance element formed from a sheet metal plate having parallel slits extending inwardly from opposite sides in staggered relationto each other to provide strips and connecting portions at the outer ends of the strips. said plate being provided with relatively large openings within each of said connecting portions and with relatively smaller openings coincident with the respective slits at the inner ends of the latter and on opposite sides of the respective connecting portions, said connecting portions being alined in parallel planes displaced in like directions substantially less than ninety degrees from the initial plane thereof, whereby said element is expanded with said strips arranged in laterally zigzagged relation to each other, a pair of insulating supporting elements penetrating said relatively large openings within said connecting portions, the walls of said openings being normally biased into frictional engagement with said insulating supporting portions, the connecting elements to retain said resistanceelement in expanded condition, and means comprisingindividual flanged thimbles of wear-resisting material interposed between the walls of certain of said openings and said supporting elements.

4. The method of forming a resistor having a resistance element formed from a sheet of metal having slits therein to provide a continuous series of strips and connecting portions at opposite ends of a strip respectively joining said strip to strips at opposite sides of said strip, which method consists in turningall of said connecting portions in a like direction to expand said element and to aline the connecting portions at opposite sides of the'element in parallel planes; whereby the adjacent strips are arranged in crisscross or laterally zigzagged relation to each other.

5. The method of forming a resistor having a resistance element formed from a sheet of metal having slits therein to provide a continuous series of strips and perforated connecting portions, the connecting portions at opposite ends of a strip respectively joining said strip to strips at opposite sides of said strip, which method consists in turning all of said connecting portions in a like direction to expand said element and to aline the connecting portions at opposite sides of the element in parallel planes, whereby the adja: cent strips are arranged in crisscross or laterally zigzagged relation to each other, and inserting supporting rods through the perforations in the connecting portions at op osite sides of said element, the walls of said forations being biased into frictional engagement with said rods to retain said element in expanded position.

6. The method of forming a resistor havin a resistance element formed from a sheet 0 metal having slits from opposite edges thereof in staggered relation to each other to provide a continuous series of strips and perforated connecting portions, which method consists in turning all of said connecting ortions in a like direction through an arc of approximately ninety degrees from the initial plane thereof whereby the adjacent strips are arranged in crisscross or laterally zigzagged relation to each extending at right angles other, inserting insulated supporting rods.

through the perforations in the connecting portions at opposite sides of the element, then permitting sald connecting portions to turn in the rev rse direction under the normal bias thereof with resultant gripping engagement of said rods by the opposite side walls of said perforations respectively, and maintaining opposite end portions of said continuous strip in fixed relation to said supporting rods respectively to retain said element in expanded position. a j

7. As an article of manufacture, a slitted 

